PD-1 deficiency impairs eosinophil recruitment to tissue during Trichinella spiralis infection

Blockade of programmed cell death 1 (PD-1) is considered a promising strategy for controlling pathogen infection by enhancing host immune cell function. Eosinophils, which play a crucial role in type 2 immune responses, are essential components of the host defense against helminth infection. Here, we investigate the role of PD-1 in eosinophilia during Trichinella spiralis infection in mice. PD-1-deficient (PD-1^-/-) mice exhibit delayed expulsion of adult worms and increased muscle larva burdens compared to wild-type mice following infection. Additionally, PD-1^-/- mice display impaired recruitment of eosinophils to parasite-invaded tissues, attributed to decreased upregulation of adhesion molecules on both eosinophils and vascular endothelium after infection. The compromised Th2 cytokine response further contributes to impaired adhesion interactions, affecting eosinophil migration and cytotoxicity against larvae in vitro within T. spiralis-infected PD-1^-/- mice. Our findings demonstrate a positive role for PD-1 in the recruitment of eosinophils, suggesting its involvement in host defense against helminth infection.